The studies are designed to increase our understanding of glomerular capillary wall antigens, either naturally occurring or "planted" there from some outside source, that can be involved in nephritogenic immune reactions. Levels of circulating antigens reactive with anti-glomerular basement membrane (GBM) antibodies are quantitated (radioimmunoassay) after a variety of manipulations (nephretomy, tissue injury, etc.) to learn more about the physiology of these antigens and factors that influence their levels. This information in turn should lead to the understanding of events that may lead to autoimmune anti-GBM antibody response. Determinations of variations in basement membrane antigens between tissues, strains, and species are being conducted as well. Studies to determine the nature of other glomerular capillary wall antigens that can be involved in nephritogenic immune reactions are also underway. At least two models have now identified in which nonclassic GBM antigens resident in the glomerular capillary wall can be the focus of an autoimmune nephritogenic antibody attack.